Field of the Invention
The present invention relates to a device or support for loading the main body of a platform containing at least one read/write transducer of a data storage medium.
The invention relates generally to the field of magnetic disc storage. Magnetic disc or data storage elements are well known in the data processing field. As a rule, one or more discs are provided, each having a magnetic coating and being mounted on a control unit for recording data on the disc and/or for reading data from the disc and updating data, as required. When the storage arrangement has several discs, they are superimposed and have the same axis of rotation. Data is written on concentric tracks on the discs by read/write transducers which move on their surface.
The read/write transducers are supported by a platform which is radially displaced above the surface of the disc by means of a linear or rotary actuator, so that the transducers can access any data contained thereon. The platform proper consists of two essential parts: one part called the "main body" of the platform which contains the transducer, and another or second part called a suspension mechanism, one end of which is secured to the main body and the other end is attached to a removable rigid arm.
The transducers contain input and/or output electrical connecting wires connected to the electronic write and/or read circuits of the disc storage with which they are associated for carrying signals to and from the disc.
Generally, the main body of a platform has the form of a relatively flat rectangular parallelepiped, whose lower face contains the transducers for reading and/or recording the data. The large upper face contains the ends of the electrical input and/or output wires connected to the transducers and the means enabling these wires to be connected to electronic read and/or write circuits of the disc storage.
In current practice, the lower face of the main body contains one or more channels having a depth which may attain several tenths of a millimeter, resulting in the existence on this face of a plurality of projecting parts called "skids" generally in the shape of a ski.
A platform of this type is illustrated and described
in U.S. Pat. No. 4,261,024 issued on Apr. 7, 1981 and entitled "Transducer". Reference may also be made to U.S. Pat. No. 4,225,891, issued on Sept. 30, 1980; U.S. Pat. No. 4,280,156 issued on July 21, 1981; and U.S. application Ser. No. 197,340, filed Oct. 15, 1980, now abandoned, for other illustrations and descriptions related to platforms of this type. The latter patents and application are all assigned to the assignee of the present invention.
The rotation of the discs leads to the existence between the lower face of the main body of the platform and the face of the disc associated therewith of a cushion of compressed air which prevents the main body from touching and, thus, from damaging the disc. It is then said that the main body and, by extension, the platform, flies above the face of the disc which is associated therewith at a distance of a few tenths of a micron. This distance between the face of the main body opposite the disc and the disc proper is called the flight attitude.
The cushion of air exerts a compressive force on the surface of the skids in a direction normal thereto and directed from the lower face to the upper face of the main body of the platform. When in flight, the dynamic equilibrium of the platform is achieved by setting up, in opposition to the force generated by the pressure of the air cushion against the surface of the skids, a force called the "loading force", which is applied to the upper face of the main body and has a modulus equal to that of the compressive force.
The loading force is usually generated by a prestressed spring secured to the rigid arm of the actuator supporting the platform. This loading force is relatively small and is of the order of 10 to 20 grams.
However, a delicate problem to be resolved with respect to supporting the platform is that of "flying" the main body. When the disc storage is not operating, the main body of the platform is positioned near the periphery of the disc and beyond said surface. This position is called the "rest position". The expression "flight stage" means the transitory stage during which the main body moves from its rest position until the moment when it is in stable flight a few tenths of a micron above the surface of the disc. This flight stage is a delicate condition mainly due to the air turbulence near the surface of the disc, particularly when the storage contains several discs.
The area defined by two circles concentric to the disc, one passing through the position of rest of the main body and the other through the point on the surface of a disc where this main body is in a stable flight, is called the "area of approach" or "putting into flight area". It is in this area that the main body descends toward the plane of the disc until it attains the flight altitude.
Devices are known in the art for loading magnetic heads for discs which contain a rigid removable arm, to which a flexible loading spring plate is affixed. In the free state, this spring plate is curved. It supports the platform at its end. The curve of the flexible spring plate is determined such as to generate a force applying the magnetic head to the disk.
The problem to be solved consists in bending the flexible plate supporting the head while the actuator is moving, radially or at an angle, depending on the case, as far as the read area of the disc and in easing this bending gradually until the loading force exerted by the flexible plate forming the spring is balanced by the cushion of compressed air which forms dynamically under the skids of the read head.
In a device of known construction, the flexible spring plate contains two symmetrical ramps which coact with stationary supports mounted on the frame and which act as a cam profile with respect to the symmetrical ramps so as to raise or to lower the flexible plate when the removable arm is shifted in relation to the disc. This loads or unloads the read/write head.
The present tendency in magnetic storage arrangements is to decrease the space occupied by the disc memories, making it possible to miniaturize the devices for loading the main bodies of the platforms. It is difficult to miniaturize prior art loading devices such as those described hereinabove.